Photographic art



Patented June 12, 1945 UNIT D ST TES PATENT o'rncs rno'rooaarmc aa'r 'Harold D. Russell and Lowell E. Muehier, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey g No Drawing. Application Sep ber 26, 1942,

. Serial No.. i=59,830 .10 Claims. (01. 95-88) This invention relates to improved photographic acid hardening fixing compositions containing an aluminum compound which acts as a hardening agent.

It is well known that acid alum hardening fixing compositions contain in addition to the alum which acts as a hardening agent, an acid, a soluble sulfite which stabilizes the thiosulfate against sulfurization, and a thiosulfate fixing agent commonly called hypo which maybe a sufficiently soluble compound of alkali, alkali'earth metals, or ammonium, amine or guanidine radicals which acts as a silver salt solvent. It has been found that an acid is necessary in order to prevent precipitation of basic compounds of the hardening agent and extend the useful-life of the fixing solution by neutralizing the alkali carried over from'the developer. For aluminum hardening fixing baths mild acetic acid has lon been used since it acts to maintain the pH suf-,

flciently low to prevent formationof sludge (basic aluminum sulfite) and does not cause early sulfurization of the fixing bath as do the stronger acids. It has been found by previous investigators that very few other acids will function satisfactorily in such an acid hardening fixingv bath. Many acids prematurely decompose the hypo to liberate sulfur or give excessive sulfur dioxide with the sulfite. Others act to decrease the hardening action of the alum. To date acetic acid has been used almost exclusively for this purpose. However, acetic acid is a liquid which is dimcult to ship. It is not suitable for any dry package preparations, and due to the war it. is notreadily available in certain areas.

This invention has for its object to provide acid aluminum hardening fixing compositions which contain a solid acidifying agent for subsequent.

combination in solution with a soluble sulfite'or bisulfite and a soluble salt of a mild aliphatic organic acid, the acidifying agent being a strong acid reacting salt which is readily available and which is satisfactory for compounding dry package fixing preparations. Another object is to provide alum type acid hardening fixing compositions which contain a cheap and readily available acidifying agent which, in the combination does not have the undesirable property of causing decomposition of the hypo or decreasing the hardening action of the hardener. Other objects will appear hereinafter.

These and other objects are accomplished .by our invention which includes an acid aluminum hardening fixing composition comprising an aluminum hardening agent and an acid sulfate which upon addition to a salt of an aliphatic acid containing two to four carbon atoms generates the corresponding free aliphatic acid.

they do not have the-undesirablecharacteristics of decomposing hypo to liberate sulfur or sulfur d oxide when used in the presence of sufllcient alkali metal sulfite or bisuliite and alkali metal salts of mild aliphatic organic acids.

is The fixing preparation of our invention ineludes, in addition to the acid sulfate, a silver salt .solvent, a soluble sulfi-te, a soluble salt of a mild aliphatic organic acid. and alum as discussed above. Examples of silver salt solvents are sodium, potassium, ammonium and guanidine thiosulfates. Examples of soluble sulfites are ammonium and alkali metal sulfltes such as sodium sulfite or bisulfite, potassium sulfite, potassium metabisulfite and ammonium sulfite or bisulfite.

Examples of suitable saltsof mild aliphatic organic acids are sodium, potassium, and ammonium acetates, propionates, and butyrate's. Examples of alum (within the meaning of the specification and claims) are sodium, potassium, and

so ammonium alums. Other aluminum compounds f such as aluminum sulfate, ichloride, acetate or propionate may be used instead of the alum.

It isfrequently inconvenient to add each of the individual components to water whenever a fixing composition is to beprepared'. This difflculty can be overcome by providing a dry packaged fixing agent including the constituents mentioned above. When preparing such dry compositions it is desirable that the alum and acid sulfate be separated in one compartment of the package or in a separate package, and the hypo (preferably anhydrous), sulfite, sodium acetate and boric acid (when desired) be incorporated in the other compartment or a separate-package. To prepare the fixing bath'the contents of these packages are then dissolved separately. the solutions cooled if at elevated temperature, and the alum-acid sulfate solution added slowly with stirring to the hypo-sulflte-acetate solution. If desired, a three compartment dry package preparation may also be provided with the hypo and sulfite in one compartment, the sodium acid sulfate, alum and boric acid (when desired) in the second and sodium acetate in the third compartment. 'Other arrangements of the ingredients are possible.

Acid aluminum hardening fixing baths can be 7 prepared to contain hypo, a soluble sulfite such 'tion of the corresponding acid.

2 i as sodium sulfite, an acid sulfate in slightly less than molecular proportion to the suliite, and alum but such solutions are not particularly practical since they do not have ample exhaustion life with the addition-pf developer in use and readilyproduce sludge and scum, They also =sulfurize or sludge readily upon standing. Approximately neutral compounds yielding acetate or similar ions and included in the solution prior to the addition of the acid sulfate'and alum'greatly improve the suifurization life of the bath. This is the result of the generation of the weaker acetic acid by the action of the strong inorganic acid sulfate on the acetate.

We have mentioned above the materials which are necessary for asatisfactory nxing bath. It

as heretofore been found that the presence of the acetate, propionate or butyrate ion is also of An example of a packaged compositionpf idry chemicals contained in two compartments is the preparation; of) 1 liter of acid a following for the hardening fixing solution: 1

- .E'zample 3 Compartment A: Grams Sodium thiosulfate (anhydrous)--- 150-240 Sodium bisulfite i5 Sodium acetate (desiccated)..--- iii)v Compartment 3: I v

Sodium acid sulfate (anhydrous) i Potassium alum 15 Instructions for MiIiMr-DIBBOIVB thecontents 1:; of compartment s in about 650 cc. of water. Disvalue in a fixing bath since it acts to present sludge formation during exhaustion. We have found that such ions act in a similar manner in our fixing compositions in addition to the genera- It is known that boron compounds in the presence of acetate or similar ions extend the pH range over which hardening action takes place and raise the pH value at which sludging occurs. include within the scope of our invention our new fixing composition as defined and containing boron compounds for these and analogous pur;

We, therefore,

solve the contents of compartment :B in about 200 cc. ofwater. Add the cool solution of compartment B slowly with stirring to the cool solution of compartment A. Dilute to make 1 liter and the resulting bath is then ready for use.

. Example 4 Compartment A: I Grams Sodium thiosulfate (anhydrous)--- 150-240 Sodium sulfite (desiccated) 18 Sodium acetate (desiccated) 20 Boric acid 1 5- l0 Compartment-B:

Sodium acid sulfate (anhydrous) poses. While the presence of boron compounds is advantageous in many (3858831881111 fixing compositions can be prepared without them and our invention 'is not restricted to the presence of th substances. Also included in our invention we consider dr packaged chemical compositions containing an acid sulfate as the acidifying agent for the preparation of acid hardener solutions adapted to be added with thiosulfates in oneor two-step hardening and flxingoperations.

toor used in conjunction.

The following are examples illustrating our invention Example 1 Water cc.. 650 Sodium thiosuli'ate (anhydrous) grams 150-240 Water solution containing sodium acid sulfate (an- This solution be added slowly with stirring to the cool solution of the preceding chemicals.

Variations in the fite (or bisulfite), sodium acetate, and sodium acid sulfate are possible provided the pH of the resulting bath is approximately 4.0 or higher, but should not exceed about 5.0 for best suliurization and exhaustion properties.

quantities'of the sodium suliii) ' solution.

. Compartment A:

Ammonium aluminum sulfate (crystals). 15

The boricacid may alternatively be placed in compartment B.

For mixing instructions, see Example 3. This example gives sufficient chemicals to enable the preparation, of 1 liter of acid hardening fixing The followingexamples are illustrative of alternative methods of packaging which permit the preparation 01 stock acid hardener solutions which may be added to thiosuliate, thiosuiiatesulfite, ofthiosulfate-bisulflte solutions to prepare acid hardening fixing baths.

- Example5 Grams Sodium acetate (desiccated) .a--. 100.0 Compartment B:

Sodium acid sulfate (anhydrous)--- IE-150.0

Potassium alum 05.0

Boric acid, crystals (when desired)- 37.5 Compartment C:

Sodium thiosulfate (anhydrous) 1,000.0

Sodium sulfite (desiccated) 00.0

To utilize this example the stock acid heroism ing solution is tents of compartment A and B in successionin 600 cc. of water at 125 F. and adding water to make 1 liter. The contents of compartment C are dissolved in added to make 4 liters. When both solutions are cool the stock hardener solution is added slowly with stirring to the thiosulfate-sulfite solution in the'proportion of parts of thiosulfate-sulflte solution. 7

Example 6 Compartment A: Grams Sodium acetate (desiccated); 100 Sodium bisulfite 3'5 Example 2 Sodium thiosulfate (crystals) grams 240.0 Sodium bisulfite ..d 15.0 Sodium acetate (desiccated), -do 20.0 Boricacid-- d 7.5 Sodium acid sulfate (20% solution) cc v 75.0 Alum grams 15.0 Water. to make iiter 1.0

Compartment B: 7

Sodium acid sulfate (anhydrous) 75 Boric acid, crystal (when-desired) 15-50 Potassium alum 75 Compartment C:

Sodium thiosulfate (mtalshnusu 1.500

prepared by dissolving the ecu about 2,400cc. of water and water 1 part of hardener to s as the generator of free aliphatic acid from the salt thereof.

2. A dry acid hardening fixing composition comprising a fixing agent, a soluble sulfite, a salt of an aliphatic acid containing two to four carbon atoms, an aluminum hardening agent and an acid sulfate as the generator of free aliphatic acid from the salt thereof.

3. A package containing the components of an acid hardening fixing agent in dry condition and including a fixing agent, a soluble sulfite, a salt of an aliphaticacid containing two to four carbon atoms, an aluminum hardening agent and an acid sulfate as the generator of free aliphatic acid from the salt thereof.

4. A package containing the components of an acid hardening fixing agent in dry condition and including a fixing agent, a soluble sulfite and a 1 salt of an aliphatic acid containing at least two but not more than four carbon atoms, an aluminum hardening agent and an acid sulfate as the main acidifying agent, the acid sulfate being seg-' regated from the other components and serving as the generator of free aliphatic acid by reaction with the salt thereof.

5. A package containing the components of an acid hardening fixing agent in dry condition and including a fixing agent, a soluble sulfite, an alkali metal salt of an aliphatic acid containing at least two but not more than four carbon atoms, aluminum alum and an alkali metal acid sulfate as the generator of free aliphatic acid by reaction with the salt thereof, the acid sulfate and the alum being segregated from the other components.

6. A dry. packaged photographic composition adapted to form an acid hardening fixing bath when mixed in aqueous solution with a fixing agent, a soluble sulfite and a salt of an aliphatic acid containing two to four carbon atoms, which composition comprises aluminum alum and an acid sulfate as the generator of free aliphatic acid by reaction with the salt thereof.

LA dry, packaged photographic composition adapted to form an acid hardening fixing bath when mixed in aqueous solution with a fixing agent, a soluble sulfite and an alkali metal salt of a member of the group consisting of acetic and propionic acids, which composition comprises a potassium aluminum alum and an alkali metal acid sulfate as the generator of acetic or propionic acid by reaction with the salt thereof.

8. A dry packaged photographic composition adapted to form an acid hardening, fixing bath when mixed in aqueous solution with a fixing agent, a soluble sulfite and a salt of an aliphatic acid containing two to four carbon atoms which composition comprises an aluminum hardening agent, and potassium acid sulfate as the generator of free aliphatic acid by reaction with the salt thereof.

9. A dry packaged photographic composition adapted for the preparation of an acid hardening fixing bath when mixed in aqueous solution with a fixing agent, a soluble sulfite, and a salt of a monobasic saturated aliphatic acid containing two to four carbon atoms comprising an aluminum alum and an acid sulfate in sufiicient' amount to react with the salt of the aliphatic acid to give an ac1d hardening fixing solution equal in properties to one utilizing the corresponding organic acid.

10. A dry packaged photographic composition adapted to form an acid hardening fixing bath when mixed in aqueous solution with a fixing agent, a soluble sulfite, and a salt of a monobasic saturated aliphatic acid containing at least two but no more than four carbon atoms, said dry packaged composition comprising an aluminum hardening agent, and anhydrous sodium acid sulfate as an acidifying agent for generating the organic acid.

HAROLD D. RUSSELL. LOWELL E. MUEHLER. 

